Although Type A behavior is a significant and independent risk factor for coronary heart disease (CHD), it appears that certain dimensions of Type A behavior are more coronary-prone than others. The widespread interest in Type A behavior underscores the importance of determining its coronary-prone dimensions. This determination will permit better approaches to the assessment of Type A behavior, the modification of Type A behavior for prevention purposes, and the study of pathogenic mechanisms that relate Type A behavior to CHD. Such a determination requires access to a study that involves a population of significant size, proper measurement of Type A behavior, and sufficient follow-up to provide an adequate incidence of CHD. The only study that fulfills these criteria is the Western Collaborative Group Study (WCGS), the data of which are housed at SRI International. An ongoing study at the University of California, Berkeley, is concerned with the further incidence of CHD that occurred in the WCGS population since that study's completion in 1969. Data from this current study will be used to examine the long-term predictive strength of specific dimensions of Type A behavior. The purpose of the proposed study is to determine the extent to which specific dimensions of Type A behavior predict the incidence, initial manifestations, and recurrent events of CHD.